“This decision is consistent with the Herman Cain we have come to know,” said SBA List president Marjorie Dannenfelser in a statement.

Cain declined to sign the pledge in June, citing a problem with one of its tentants in a statement: “(T)he fourth requirement demands that I ‘advance’ the Pain-Capable Unborn Child Protection Act. As president, I would sign it, but Congress must advance the legislation.”

Since then, many have questioned Cain’s pro-life stance on abortion after a series of unclear statements that peaked when Piers Morgan prodded the candidate about the issue on CNN.

“What Piers Morgan was trying to do was to pigeonhole me on, ‘Well, what if this was your granddaughter?'” Cain told The Des Moines Register in one such statement. “You know what? If it’s my granddaughter? Yes, this is my official position, and it’s always been that. If it’s my granddaughter? I used the word ‘choice.’

With a late-signing of SBA’s pledge, Cain looks to solidify his pro-life credentials with social conservatives once and for all.

Of the top eight Republican candidates, only the field’s moderates –Mitt Romney and Jon Huntsman — have yet to sign the pledge.